I. Field of the Invention
This invention relates generally to portable machining lathes, and more particularly to a machine for re-facing worn, corroded, pitted and leaking gasket seat surfaces of oval manways commonly found on pressurized industrial vessels such as tanks, steamlines, pipelines, etc.
II. Discussion of the Prior Art
Industrial facilities, such as power generating plants, petroleum processing plants and other like facilities have high pressure tanks and pipelines that commonly incorporate sealed entrance ports called manways. Maintenance personnel can use the manways to gain access to the interior of the vessel.
In many instances, these access ports have an oval or elliptical profile. With time, the gasket seat surface between the manway and the vessel may become pitted, corroded and worn to the point where leaks develop. When this happens, it becomes necessary to reface the gasket seat area. To minimize the downtime of the industrial production, it is imperative that the re-facing be accomplished in situ.
One approach for re-facing oval manways in the past has been to use a grinder such as the Oval Manway Seat Grinder commercially available from the D. L. Ricci Corp., the assignee of the present application. This grinder produces a very smooth, fine finish on the manway seat area. However, in some applications, such a smooth surface is disadvantageous. More particularly, in high pressure applications, the gasket used between the manway and the vessel can be extruded radially outwardly due to the high pressures encountered. It is, therefore, desirable in such high pressure applications that the re-surfacing of the gasket seat area result in a slightly ridged surface resembling the somewhat concentric grooves of a phonograph record. This roughened surface has been found to inhibit gasket extrusion even under very high pressures developed within the vessel in question.
It is unduly heavy, making it difficult to set up from a location outside of the vessel. Also, the opening of the oval manway is substantially occluded, making adjustments from outside of the vessel and observation of the surface being machined difficult to do.
The present invention provides an improved machine for re-surfacing the face of an oval manway gasket seat. It includes a housing having first and second oval-shaped major surfaces having an oval-shaped central opening that is formed through the thickness dimension of the housing. The housing is designed to fit within and be supported by an oval manway to be machined. It has a first track member affixed to the first major surface in surrounding relation to the oval-shaped central opening. Likewise, a second track member is disposed on the second major surface, also in surrounding relation to the central opening. A drive means supported by the housing and cooperating with the first track member causes the drive means to orbit the oval-shaped central opening when the drive means is energized. The drive means carries a bracket member having an arm that extends through the oval-shaped central opening. The arm pivotally supports a link member that is operatively coupled to the second track member and that link member carries a machine tool slide assembly in an orbital path defined by the second track member. The machine tool slide assembly supports a cutting tool for engaging the face of the oval manway.
The machine tool slide assembly comprises a cam actuated feed screw for incrementally translating the cutting tool in a radial direction as the machine tool slide assembly is carried in its orbital path.
Because the central opening of the housing does not become blocked by the tool slide assembly and structure supporting it, an operator, from the outside, can reach through the central opening to make depth-of-cut adjustments and can selectively engage and disengage the cam actuated lead screw that controls the radial translation of the cutting tool. Moreover, because the oval manway is not appreciably blocked or occluded by the facer assembly, the surface being worked can be readily viewed.